Cross drive for lift jack apparatus

ABSTRACT

A lift jack apparatus for a camper body includes lift jack units rigidly secured to each corner of the camper, each jack unit including a lift mechanism, and a cross drive assembly is releasably connected between adjacent pairs of jack units to transmit actuation of one unit through the lift mechanism of the other unit in loading and unloading a camper body onto and from a truck bed.

0 United States Patent [151 3,640,502

Bargman, Jr. Feb. 8, 1972 [54] CRDSS DRIVE FOR LIFT JACK 2,553,156 5/1951 Woodward ..254/92 X APPARATUS 3,338,554 8/1967 Gostomski.. ...254/45 X [72] Inventor: Dale L. r 1 m g Jr. Brownfield, Colo. 3,567,271 3/1971 Gostomski ..254/45 [73] Assignee: Colorado Leisure Products, Inc., Broom- Primary Examiner-Andrew R. Juhasz field, Colo. Assistant Examiner-David R. Melton [22] Filed: June 1, 1970 Attorney-Reilly and Lewis [2 pp 42,312 [57] ABSTRACT A lift jack apparatus for a camper body includes 11ft jack units [52 U.S. C1. ..254 45, 254/89 R rigidly secured to each come, f the camper, each jack unit [51] Int. Cl. "B661 7/26 including a f mechanism and a cross drive assembly is of Search 86, 89, 92 releasably connected between adjacent of units m transmit actuation of one unit through the lift mechanism of [56] References Clted the other unit in loading and unloading a camper body onto UNITED STATES PATENTS and from a truck 2,550,801 5/1951 Geerds ..254/86 X 17C1auns' ,7Drawmg' Figures CROSS DRIVE FOR LIFT JACK APPARATUS SPECIFICATION This invention relates to novel and improved lift jack apparatus, and more particularly relates to a cross drive for simultaneously activating two or more lift jack units in loading and unloading a camper body onto and from a truck bed.

US. Pat. No. 3,314,655, assigned to the assignee of the present invention, describes typical lift jack apparatus in which individual jack units are successively actuated for lifting or lowering a camper between the ground and the elevated height necessary for placement on a truck bed. The units described and similar types of units are advantageously utilized from the standpoint of efficiency and dependability in lifting and supporting a camper. Moreover, rigid fastening of the lift jack units to the four vertical comers of the camper is particularly advantageous in lifting and lowering the larger camper bodies in present-day use. Nevertheless, utilization of four sets of lift jack units, one at each comer of the camper body, presents the problem of successive lifting of each jack unit by a single operator which is time consuming, imposes severe strain on the other lift jack units and on the camper body itself.

It is an object of the present invention to provide for a simplified but highly effective, low-cost method and means for the synchronized lifting and lowering of a load through sequential actuation of a plurality of lift units and in such a way as to minimize strain imposed both on the lift units and on the load.

It is another object of the present invention to provide for novel and improved means to facilitate lifting of a camper body to the elevated height required and specifically in such a way that actuation of one jack unit is transmitted automatically to at least one of the other jack units to effect simultaneously the lifting of two corners of the camper body.

It is still a further object of the present invention to provide for a novel and improved lift jack apparatus incorporating a cross drive assembly between adjacent pairs of lift jack units to automatically transmit actuation of one of the units into the other of each pair of units; and further wherein the cross drive assembly is quickly releasable but positively engageable with the lift mechanisms to synchronize lifting and lowering of opposite ends of the camper body in a dependable and highly effective manner.

In the preferred form of the present invention, lift jack units are rigidly clamped through offset brackets to the vertical corners of a camper body, each lift jack unit having a lift mechanism which is vertically displaced under the rotation of a transversely extending drive shaft. In order to couple together adjacent pairs of jack units for synchronous lifting of one end or side of the camper, adjacent pairs of the units have their drive shafts aligned in facing relation to one another for engagement by a cross drive assembly. An important feature resides in the construction and arrangement of the cross drive assembly between the drive shafts, the cross drive having a spring-loaded, elongated coupling member with pivotal socket portions at opposite ends to receive the drive shafts. The cross drive can be contracted to permit alignment of the socket end portions with the shafts then released to permit expansion of the assembly with the drive shafts snugly inserted within the socket end portions.

Preferably, the spring-loaded coupling member is defined by square telescoping sleeves, and the socket end portions are connected by means of a universal joint to opposite ends of the telescoping sleeves. Accordingly, rotation of one drive shaft is transmitted through the cross drive to the other shaft to effect synchronous displacement and simultaneous lifting of one end or side of the camper body. Since the cross drive assembly is quickly engageable and releasable, one cross drive may be supplied for use at both ends or sides, or cross drives may be mounted between each of the adjacent lift jack units; also, the quick releasability of the cross drive assembly facilitates rapid disassembly for storage within the camper body when the apparatus is not in use.

The foregoing and other objects, advantages and features of the present invention will become more apparent from the following more particular description of the invention when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating the mounting, disposition and arrangement of a preferred form of lift jack apparatus on a camper body in accordance with the present invention.

FIG. 2 is an assembly view illustrating the cross drive assembly mounted between an adjacent pair of lift jack units with portions broken away and shown partially in section.

FIG. 3 is a view in more detail of the preferred form of comer bracket forming a part of the present invention.

FIG. 4 is a sectional view taken about lines 4-4 of FIG. 3.

FIG. 5 is an enlarged cross-sectional view taken about lines 5-5 of FIG. 2.

FIG. 6 is an enlarged cross-sectional view taken about lines 6-6 of FIG. 2; and

FIG. 7 is an enlarged perspective view of a socket end portion and U-joint on the cross drive assembly.

Referring in more detail to the drawings, there is shown in FIG. 1 the preferred manner of mounting and placement of a lift jack apparatus on a camper body C. Typically, the camper body is of generally rectangular configuration and, to facilitate placement on the bed of a pickup truck, opposite sides of the body are recessed as at 10 to accommodate the side rails of the truck bed. In addition, the front end 12 is provided with an overhand 13 which extends over the cab section of the vehicle. The rear end 14 of the camper may project beyond the back end of the truck and, although not shown, is usually provided with an entry door into the camper. Of course, the camper body shown is merely representative of various types of commercially available campers on the market and is described merely as a setting for the present invention.

In accordance with the present invention, the lift jack apparatus is comprised of a set of four lift jack units 20 each unit being rigidly fastened to one of the four comers of the camper body by means of a comer bracket 22, each corner bracket consisting of an angle iron 23 having a flange 24 across its lower end which fits beneath and is secured to the bottom corner edge of the camper for added rigidity and stability. Because of the particular configuration of the camper body, the exact placement of the bracket on the comer may vary and, for example, it will be noted that the brackets 22 at the front corners of the camper are raised to engage the lower comer edge formed by the lateral wings on the recessed portions 10; whereas, the rear comer brackets 22 are somewhat longer and have bottom flanges 24' engageable with the bottom comer edge at each rear comer of the camper. As shown in FIGS. 3 and 4, each of the brackets 22 and 22' is correspondingly provided with spaced upper and lower generally C-shaped bands 25 and 25, respectively, the bands 25 projecting forwardly from the front brackets 22 and the bands 25 projecting rearwardly from the rear brackets 22' when installed on the camper. Specifically, each band includes a circular portion 26 with spaced, rearwardly divergent connecting end portions 27. End portions 27 are suitably attached as shown by screws 32 to opposite sides of a generally U-shaped mounting plate 28, the latter permanently attached, such as, by welding to one side of the bracket 22. The closed end 29 is of a concave configuration to complete and to conform to the inner periphery of the circular portion 26.

Each lift jack unit comprises inner and outer telescoping tubes 30 and 31, as best shown from FIG. 2, and a lift mechanism generally designated at 34 is housed within the outer tube 31 to vertically displace the inner tube 30 with respect to the outer stationary tube 31 under the control of the rotary drive assembly 35. In the preferred form, the outer tube is inserted through the bands 25 and 25' and fastened thereto by suitable means, such as, set screws 36 which extend through the circular portion to engage the outer tube and yfirmly clamp the tube in position on the bracket. The inner tubular member 30 is inserted in close-fitting relation through the lower open end of the outer tube 31 and is provided with an enlarged circular base plate or pad 38 which closes the lower end of the tube 30. A drive nut 40 is mounted at the upper extreme end of the inner tube 30 and includes an internally threaded sleeve 41 which threadedly engages an inner drive screw 42. The inner drive screw 42 includes a smooth surfaced upward extension 44 of reduced diameter upon which is mounted a thrust bearing 45 and a generally U- shaped saddle support 46 welded to the top of the tubular outer member 31 for the drive assembly 35. Specifically, the drive assembly includes bevel gears 47 and 48, the pinion 47 being keyed to a cross shaft 50 by pin 51, and the cross shaft in turn extends transversely of the vertical axis of the jack unit and is joumaled in opposite sides of the support 46. The bevel gear 48 is keyed by a pin 52 to the upper extremity of the reduced extension 44 whereby rotation of the cross shaft is imparted through the bevel gearing to the inner drive screw 42 so as to effect vertical or linear displacement of the inner tube 30 through its drive nut 40 along the length of the drive screw 42 between a retracted position, as shown in full, and an extended position, as shown dotted in FIGS. 1 and 2. An unthreaded area at the lower extremity of the drive screw 42 limits the extension of the drive nut beyond that point.

In the relation viewed in FIG. 2, each cross shaft 50 has a circular shaft end portion 56 with a transverse drive pin 57 on the right side and a square end portion 58 on the left side, the latter dimensioned for insertion into a drive socket 60 which is affixed by a universal joint 61 to the end of a rotary drive member. As represented in FIG. 1, the drive member preferably takes the form of a manual crank 62 or electric drill motor 63, each utilizing an elongated drive rod 64 with a drive socket 60 universally connected by the joint 61 at one or both ends to transmit driving torque from the crank or drill motor to the drive rod shaft end portion 58. The lower end also includes a suitable fitting for releasable driving connection between the end of the drive rod, or universal joint at the end of the drive rod, and the end of the drill motor 63.

An important feature of the present invention resides in the use of a cross drive assembly 70 which is dimensioned for extension between the cross shafts 50 in order to transmit the rotation of one cross shaft to the other and to impart synchronous lifting or lowering to each pair of the lift jack units and avoid the necessity of sequential lifting of each comer of the camper body. For this purpose, the cross drive assembly includes an intermediate, spring-loaded coupling which is preferably defined by inner and outer telescoping sleeves 71 and 72, respectively, provided with universal joints 74 and 75 at opposite extreme ends. As noted from FIG. 5, the sleeves are square or rectangular in cross section for the purpose of transmitting rotational movement therebetween; or of course may be circular tubes keyed together for the same purpose. In addition, the outer sleeve 72 is provided with a roll pin 76 adjacent to its universal joint 74 to serve as a limit stop for a coiled compression spring 77 with the opposite end of the spring abutn'ng the inner free end of the inner sleeve 71. Asshown in FIG. 7, each of the universal joints 74 and 74 correspondingly includes double pivots 79 and 80 perpendicular to one another and at opposite ends of a pivot link 81 with the inner pivot 79 mounted in a fitting 82 which is welded or otherwise securely affixed to the end of the sleeve 71 or 72. The opposite end of universal joint 74 has a socket end portion 84 provided with an inner, square-sectioned cavity 85 together with a transverse slot 86 to receive a drive pin 57 on the end portion 56 of the cross shaft so as to be keyed for rotation therewith. However, the universal joint 75 has a socket end portion 88 similarly provided with an inner central cavity 85, square in cross section, but is not slotted and is sized to snugly receive the square end 58 of the other cross shaft.

Considering each pair of lift jack units at the front and rear ends of the camper body, it will be noted that the cross shafts are horizontally aligned with an inner end portion 56 on one cross shaft in facing relation to an end portion 58 on the other cross shaft. The cross drive assembly issized to be of a length, when the spring member 77 is fully extended, approximating the distance between the vertical axes of the pair of lift jack units to be coupled together, such as, those at the front and rear comers of the camper body. Accordingly, to mount the cross drive assembly in driving relation between the lift jack units, it is necessary to contract the cross drive assembly against the urging of its spring in order to permit the socket end portions to be aligned with the inner ends of the cross shafts for insertion of the cross shafts into the socket end portions when the cross drive assembly is extended under the urging of the spring. Once installed, rotation of one of the cross shafts by the drive member either to lift or lower the inner tube assembly is transmitted to the other lift jack unit through the cross drive to correspondingly lift or lower the other lift jack unit. It is important that the cross shafts be horizontally aligned, or substantially so, for most efiective coupling and synchronous lifting of each pair of lift jack units, although utilization of the joints 74 and 75 at the ends of the cross drive will compensate for any minor misalignment between the shafts 50.

In use, and assuming that the camper body is positioned at rest on the ground,as shown in full in FIG. I, through successive driving of the front and rear corner lift jack pairs in unison by the drive member, the front and rear end sections of the camper body are successively lifted until the camper body reaches the elevated height necessary to permit the truck to be backed into position beneath the camper body. Thereafter, the lift jack units may be dropped or lowered until the truck bears the entire weight of the camper. Conversely, to remove the camper body from the truck, the lift jack units are raised a slight distance to permit the truck to be removed from beneath the camper body with the weight of the camper body supported entirely by the lift jack apparatus, after which the front and rear comer jacks can be successively lowered to the ground position. The drive sockets 60 and universal joints 61 for releasable connection of the rotary drive member preferably correspond to the socket end portion 84 and universal joint 74, as shown in FIG. 7, so as to permit driving of the jack assembly at either end of the drive shaft 50 as described. The added advantage of the elongated rotary drive member is that it will permit the operator to lift and lower the camper between the ground and elevated positions without the aid of a stool or ladder, and the elongated drive rod with the universal joint at one or both ends will serve to effectively couple the drive crank or motor to the drive shaft over a widely varying angle as the camper is moved upwardly or downwardly. Utilization of a slotted, square cavity on the socket end portion 60 will enable the operator to utilize a unidirectional drive motor for the purpose of lifting the jack units, for example, by engaging the drive pin on a round shaft end 56, or lowering the jack units by engaging a square shaft end 58 at the opposite end of the same or other lift jack unit. In other words, a reversible motor drive is not required and the jack units may be operated singly or in unison for lifting and lowering the camper by selective engagement with opposite ends of the drive shaft.

The cross drive assemblies may be quickly released from the lift jack units when not in use simply by contraction of the telescoping sleeves, in the manner previously described, and removal from the cross shafts for storage within the camper. It will further be evident that by virtue of the quick releasability of the cross drive assembly, only one assembly is necessary for each set of lift jack units and may be easily interchanged for mounting and placement between each pair of lift jack units for successive lifting or lowering of the camper body. Of course, each unit may be independently driven simply by removal of the cross drive, for example, if the camper is on uneven ground and it is necessary to extend the units to different lengths.

Although a double pivot or universal joint is shown between the socket end portions and intermediate coupling of the cross drive assembly, single pivotal connections may be utilized but are not as effective as the universal joint in compensating for misalignment and efficient transmission of driving forces between the liftjack units.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit of the invention.

lclaim:

l. The combination with a generally rectangular load to be lifted of a lift jack apparatus comprising:

a lift jack unit secured to each vertical corner of the load,

each of said liftjack units including a vertically displaceable lift mechanism and rotatable drive means extending transversely of said lift mechanism rotatable about a horizontal axis of rotation to vertically displace said lift mechanism, adjacent pairs of said lift jack units arranged with said drive means horizontally aligned in facing relation to one another, and

a cross drive assembly adapted for extension between each adjacent pair of lift jack units, said cross drive assembly including an elongated coupling member having opposite pivotal end portions, each of said end portions releasably engageable with one of said rotatable drive means of an adjacent pair of lift jack units whereby to transmit rotation of one of said drive means through said cross drive assembly for synchronous rotation of the other of said drive means.

2. The combination according to claim 1, said cross drive assembly being further characterized by including biasing means normally urging said pivotal end portions in opposite directions to releasably but firmly engage each of said drive means.

3. The combination according to claim 1, said drive means including a drive shaft on each of said liftjack units with the drive shafts of adjacent pairs horizontally aligned with one another, and said pivotal end portions being defined by socket end portions each dimensioned to receive an end of a drive shaft on one of said lift jack units for driving engagement therewith.

5. The combination according to claim 3, further including a universal joint pivotally interconnecting each of said socket end portions to an opposite end of said elongated coupling member.

5. The combination according to claim 1, said elongated coupling member being defined by telescoping inner and outer concentric spring-loaded sleeve members, said inner sleeve member being outwardly biased toward an extended position with respect to said outer sleeve member.

6. Lift jack apparatus for a camper body wherein lift jack units are secured in lift-engaging relation to each of the four vertical corners of said camper body on a transport vehicle, each of said lift jack units including a lift mechanism, and the lift mechanisms of adjacent pairs of said lift jack units including transverse drive shafts horizontally aligned in facing relation to one another, the improvement comprising:

a cross drive assembly drivingly interconnecting each of said adjacent pairs of lift jack units, said cross drive assembly including a coupling member defined by telescoping sleeves and means biasing said sleeves to a total effective length greater than the distance between said adjacent pairs of lift jack units, and socket end portions pivotally connected to opposite ends of said sleeves, each dimensioned for insertion of the inner facing end of a drive shaft therein and keyed for rotation with the drive shaft whereby rotation of one of said drive shafts is imparted through said cross drive assembly to the other of said drive shafts for synchronous displacement of said lift mechanisms on adjacent pairs of said lift jack units.

7. Lift jack apparatus according to claim 6, further including corner brackets rigidly interconnecting each of said lift jack units to a vertical corner of said camper body, each comer bracket having a bottom horizontal flange abutting the underside of the camper at the lower edge of each vertical corner, each lift jack unit including an outer tubular member fastened in stationary relation to said bracket and an inner concentric tubular member slidable in telescoping relation through said outer tubular member, said lift mechanism for each unit further including a drivescrew displaceable by rotation of a drive shaft to vertically displace said inner tube with respect to the outer tube in lifting and lowering said camper body.

8. Lift jack apparatus according to claim 7, the lift mechanism of each lift jack unit further including a generally U-shaped, upstanding support for said drive shaft, said support being affixed to the upper end of said outer tube, bevel gear members arranged on said support and keyed to said drive shaft and drivescrew, respectively, to transmit rotation of said drive shaft to said drive screw, and a drive sleeve affixed to said inner tube and threadedly engageable with said drive screw to impart linear movement to said inner tube in response to rotation of said drivescrew.

9. Lift jack apparatus according to claim 6, one end of each drive shaft being generally rectangular in cross section, and the other end of each drive shaft being generally circular in cross section and having a transverse drive pin thereon, and the socket end portions on the cross drive assembly each having a generally rectangular cavity sized for close-fitting insertion of the rectangular end of the drive shaft, and one of said socket end portions having drive pin-receiving slots communicating with the cavity for driving connection with the other end of the drive shaft.

10. Lift jack apparatus for a generally rectangular camper body comprising a plurality of lift jack units, each lift jack unit including inner and outer telescoping tube members, said outer tube member rigidly secured to each of the four vertical corners of said camper body, a lift mechanism mounted on said outer tube member including a drive shaft and a drivescrew drivingly engaging said inner tube vertically through the lower open end of said outer tube, the lift mechanisms of adjacent pairs of said lift jack units having said drive shafts horizontally aligned in facing relation to one another, drive means for rotating one of said drive shafts on each pair of lift jack units whereby to adjustably raise and lower said inner tube member, and

a cross drive assembly drivingly interconnecting each of said pairs of adjacent lift jack units, said cross drive assembly including a coupling member defined by telescoping sleeves, means biasing said sleeves to a total effective length greater than the distance between said adjacent pairs of lift jack units, and socket end portions pivotally connected to opposite ends of said sleeves, each dimensioned for insertion of the end of a drive shaft therein and keyed for rotation with the drive shaft whereby rotation of one of said drive shafts is imparted through said cross drive assembly to the other of said drive shafts for synchronous displacement of said lift mechanisms on adjacent pairs of said lift jack units.

11. Lift jack apparatus according to claim 10, said inner tube member including a ground-engaging base plate thereon and a drive nut interposed between said drivescrew and said inner tube to vertically displace said inner tube in response to rotation of said drivescrew.

12. Lift jack apparatus according to claim 11, said drive screw arranged for axial extension in inner spaced concentric relation to said inner tube member.

. 13. Lift jack apparatus according to claim 10, further including a bracket fastened to each vertical tube member to each bracket.

14. Lift jack apparatus according to claim 13, each band defined by a generally C-shaped clamp having a pair of spaced connecting end portions at its terminal ends, and spacer means for mounting each clamp on said bracket whereby to clamp said outer tube member in spaced relation to said bracket.

l5. Lift jack apparatus according to claim 14, said spacer means defined by a generally U-shaped mounting plate having opposite sides converging in a lateral direction away from connection to said bracket and terminating in a closed end portion having a concave surface conforming to the curvature of said clamp, and the connecting end portions of said clamp diverging rearwardly for connection to the convergent sides of the mounting plate with the closed end of the mounting plate aligned with the inner surface of said clamp, and adjustable means on said clamp engageable with said outer tube to urge it against the closed end of said mounting plate.

16. Lift jack apparatus for a camper body wherein lift jack units are secured in lift-engaging relation to each of the four vertical comers of said camper body on a transport vehicle, each of said lift jack units including a lift mechanism, and the lift mechanism of each lift jack unit including a transverse drive shaft rotatable to activate said lift mechanism is lifting and lowering the camper body, the improvement comprising,

a rotary drive member including an elongated drive rod, drive means engageable with one end of the drive rod, and a universal joint having a drive socket releasably but drivingly connecting the opposite end of the drive rod and one end of a drive shaft, the drive rod being of sufficient length to permit lifting and lowering of the camper body between the ground and the elevated height necessary for placement on a truck bed.

l7. Lift jack apparatus according to claim 16, one end of each drive shaft being generally rectangular in cross section, and the other end of each drive shaft being generally circular in cross section and having a transverse drive pin thereon, said drive socket having a generally rectangular cavity sized for close-fitting insertion of the rectangular end of the drive shaft and having drive pin-receiving slots communicating with the cavity for driving connection with the other end of the drive shaft. 

1. The combination with a generally rectangular load to be lifted of a lift jack apparatus comprising: a lift jack unit secured to each vertical corner of the load, each of said lift jack units including a vertically displaceable lift mechanism and rotatable drive means extending transversely of said lift mechanism rotatable about a horizontal axis of rotation to vertically displace said lift mechanism, adjacent pairs of said lift jack units arranged with said drive means horizontally aligned in facing relation to one another, and a cross drive assembly adapted for extension between each adjacent pair of lift jack units, said corss drive assembly including an elongated coupling member having opposite pivotal end portions, each of said end portions releasably engageable with one of said rotatable drive means of an adjacent pair of lift jack units whereby to transmit rotation of one of said drive means through said cross drive assembly for synchronous rotation of the other of said drive means.
 2. The combination according to claim 1, said cross drive assembly being further characterized by including biasing means normally urging said pivotal end portions in opposite directions to releasably but firmly engage each of said drive means.
 3. The combination according to claim 1, said drive means including a drive shaft on each of said lift jack units with the drive shafts of adjacent pairs horizontally aligned with one another, and said pivotaL end portions being defined by socket end portions each dimensioned to receive an end of a drive shaft on one of said lift jack units for driving engagement therewith.
 4. The combination according to claim 3, further including a universal joint pivotally interconnecting each of said socket end portions to an opposite end of said elongated coupling member.
 5. The combination according to claim 1, said elongated coupling member being defined by telescoping inner and outer concentric spring-loaded sleeve members, said inner sleeve member being outwardly biased toward an extended position with respect to said outer sleeve member.
 6. Lift jack apparatus for a camper body wherein lift jack units are secured in lift-engaging relation to each of the four vertical corners of said camper body on a transport vehicle, each of said lift jack units including a lift mechanism, and the lift mechanisms of adjacent pairs of said lift jack units including transverse drive shafts horizontally aligned in facing relation to one another, the improvement comprising: a cross drive assembly drivingly interconnecting each of said adjacent pairs of lift jack units, said cross drive assembly including a coupling member defined by telescoping sleeves and means biasing said sleeves to a total effective length greater than the distance between said adjacent pairs of lift jack units, and socket end portions pivotally connected to opposite ends of said sleeves, each dimensioned for insertion of the inner facing end of a drive shaft therein and keyed for rotation with the drive shaft whereby rotation of one of said drive shafts is imparted through said cross drive assembly to the other of said drive shafts for synchronous displacement of said lift mechanisms on adjacent pairs of said lift jack units.
 7. Lift jack apparatus according to claim 6, further including corner brackets rigidly interconnecting each of said lift jack units to a vertical corner of said camper body, each corner bracket having a bottom horizontal flange abutting the underside of the camper at the lower edge of each vertical corner, each lift jack unit including an outer tubular member fastened in stationary relation to said bracket and an inner concentric tubular member slidable in telescoping relation through said outer tubular member, said lift mechanism for each unit further including a drivescrew displaceable by rotation of a drive shaft to vertically displace said inner tube with respect to the outer tube in lifting and lowering said camper body.
 8. Lift jack apparatus according to claim 7, the lift mechanism of each lift jack unit further including a generally U-shaped, upstanding support for said drive shaft, said support being affixed to the upper end of said outer tube, bevel gear members arranged on said support and keyed to said drive shaft and drivescrew, respectively, to transmit rotation of said drive shaft to said drive screw, and a drive sleeve affixed to said inner tube and threadedly engageable with said drive screw to impart linear movement to said inner tube in response to rotation of said drivescrew.
 9. Lift jack apparatus according to claim 6, one end of each drive shaft being generally rectangular in cross section, and the other end of each drive shaft being generally circular in cross section and having a transverse drive pin thereon, and the socket end portions on the cross drive assembly each having a generally rectangular cavity sized for close-fitting insertion of the rectangular end of the drive shaft, and one of said socket end portions having drive pin-receiving slots communicating with the cavity for driving connection with the other end of the drive shaft.
 10. Lift jack apparatus for a generally rectangular camper body comprising a plurality of lift jack units, each lift jack unit including inner and outer telescoping tube members, said outer tube member rigidly secured to each of the four vertical corners of said camper body, a lift mechanism mounted on said outer tube member includiNg a drive shaft and a drivescrew drivingly engaging said inner tube vertically through the lower open end of said outer tube, the lift mechanisms of adjacent pairs of said lift jack units having said drive shafts horizontally aligned in facing relation to one another, drive means for rotating one of said drive shafts on each pair of lift jack units whereby to adjustably raise and lower said inner tube member, and a cross drive assembly drivingly interconnecting each of said pairs of adjacent lift jack units, said cross drive assembly including a coupling member defined by telescoping sleeves, means biasing said sleeves to a total effective length greater than the distance between said adjacent pairs of lift jack units, and socket end portions pivotally connected to opposite ends of said sleeves, each dimensioned for insertion of the end of a drive shaft therein and keyed for rotation with the drive shaft whereby rotation of one of said drive shafts is imparted through said cross drive assembly to the other of said drive shafts for synchronous displacement of said lift mechanisms on adjacent pairs of said lift jack units.
 11. Lift jack apparatus according to claim 10, said inner tube member including a ground-engaging base plate thereon and a drive nut interposed between said drive screw and said inner tube to vertically displace said inner tube in response to rotation of said drivescrew.
 12. Lift jack apparatus according to claim 11, said drivescrew arranged for axial extension in inner spaced concentric relation to said inner tube member.
 13. Lift jack apparatus according to claim 10, further including a bracket fastened to each vertical corner of said camper body, each bracket including spaced upper and lower bands releasably clamping said outer tube member to each bracket.
 14. Lift jack apparatus according to claim 13, each band defined by a generally C-shaped clamp having a pair of spaced connecting end portions at its terminal ends, and spacer means for mounting each clamp on said bracket whereby to clamp said outer tube member in spaced relation to said bracket.
 15. Lift jack apparatus according to claim 14, said spacer means defined by a generally U-shaped mounting plate having opposite sides converging in a lateral direction away from connection to said bracket and terminating in a closed end portion having a concave surface conforming to the curvature of said clamp, and the connecting end portions of said clamp diverging rearwardly for connection to the convergent sides of the mounting plate with the closed end of the mounting plate aligned with the inner surface of said clamp, and adjustable means on said clamp engageable with said outer tube to urge it against the closed end of said mounting plate.
 16. Lift jack apparatus for a camper body wherein lift jack units are secured in lift-engaging relation to each of the four vertical corners of said camper body on a transport vehicle, each of said lift jack units including a lift mechanism, and the lift mechanism of each lift jack unit including a transverse drive shaft rotatable to activate said lift mechanism in lifting and lowering the camper body, the improvement comprising, a rotary drive member including an elongated drive rod, drive means engageable with one end of the drive rod, and a universal joint having a drive socket releasably but drivingly connecting the opposite end of the drive rod and one end of a drive shaft, the drive rod being of sufficient length to permit lifting and lowering of the camper body between the ground and the elevated height necessary for placement on a truck bed.
 17. Lift jack apparatus according to claim 16, one end of each drive shaft being generally rectangular in cross section, and the other end of each drive shaft being generally circular in cross section and having a transverse drive pin thereon, said drive socket having a generally rectangular cavity sized for close-fitting insertion of the rectangular end of the drive shaft and having drive pin-receiving slots communicating with the cavity for driving connection with the other end of the drive shaft. 